A low-profile microwave device integrating dual-polarized filtering antenna and lowpass filter

This paper presents a low profile, multifunctional microwave device, which behaves either as a dual-polarized filtering antenna or as a lowpass filter. For the dual-polarized filtering antenna, two introduced quarter-wavelength open-circuit stubs can generate a radiation null at the lower frequency stopband to obtain good frequency selectivity. Moreover, to improve the out-of-band radiation suppression level at high frequencies, the C-shaped short-circuit stubs and U-shaped metal strips are loaded at feeding structures. In the case of the filter, the feeding network and part of the patchwork together to form a lowpass filter. The overall height of the designed microwave device is only 0.05 wavelengths at 2.6 GHz. The results show that the average gain is 8.09 +/- 0.54 dBi in the antenna frequency band with out-of-band gain suppression level of 25.1 dB. Moreover, when the device act as a lowpass filter, the insertion loss between the two ports is less than 0.7 dB at the lower working band.